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A load cell is a type of transducer that converts force into electrical energy. This transformation occurs in two stages; the force is first sensed by a strain gauge then is converted into an electrical signal through the alteration of the electrical resistance of a connected wire. Load cells are typically used in a number of common scenarios, including the electronic weighing of trucks and train cars, and even in smaller home electronic weight scales.
When force is applied to a load cell, it deforms the strain gauge or gauges installed within the cell. A strain gauge is a device which changes shape depending on the amount of force being applied. As more force is applied to the strain gauge, it deforms further and further. Through its deformation, it changes the amount of electricity that flows through the attached line; this results in the production of an increased level of electrical current, generating electricity from the initial mechanical force being applied to the load cell.
An electronic scale can provide a good example for how a load cell works. As an individual steps on the scale, his or her body weight disrupts the strain gauges mounted in the scale. This, in turn, disrupts the electrical signals flowing through the scale. By measuring the disruption — the change from the baseline value — the scale is able to determine how much weight is being applied to it, providing an accurate reading of how much the user weighs.
A load cell typically contains more than one strain gauge. This allows the force to be accurately detected and converted even if the application of force is not consistently located on the center of any particular gauge. In a load cell with multiple strain gauges, these gauges are normally arranged in a diamond formation known as a Wheatstone Bridge formation, which looks something like a two-dimensional square which has been tilted 45 degrees to one side. There are four strain gauges in a Wheatstone Bridge configuration, with one of the gauges located in the center of each side of the square.